Polycarbonate is a thermoplastic, it's strong and impact resistant (It's used in the making of bullet proof glass and compact discs) temperature resistant and it can be extruded (at the right temperature). It can be bent and formed while cold without cracking or deform and it is also very optically 'crystal' clear to visible light (opaque to UV light), but it's actually not very easy to keep it clear during extrusion, see below -
Polycarbonate is an interesting material for 3D printing, it seems to have low warp, strong in filament form so is easily extruded using common extruder drive systems.